Froth flotation



United States Patent I Compania Salitrera Anglo-Lautaro (Anglo-LautaroNitrate Corporation), New York, N. Y.

N 0 Drawing. Application November 15, 1952, Serial No. 320,832

4 Claims. (Cl. 209-166) This invention relates to the separation andseparate recovery of water-soluble minerals or inorganic compounds byfroth flotation. More particularly, the invention contemplates theprovision of an improved process or method for treating a productcontaining or consisting essentially of solid sodium nitrate, solidpotassium nitrate and solid magnesium sulphate heptahydrate to produceor obtain (1) a concentrate containing the potassium nitrate inpredominant proportion or consisting essentially of potassium nitrate,(2") a concentrate containing the sodium nitrate in predominantproportion or consisting essentially 0t sodium nitrate and (3) aconcentrate containing magnesium sulphate heptahydrate in predominantproportion or consisting essentially of magnesium sulphate heptahydrate.

Products containing mixtures of solid potassium nitrate, solid sodiumnitrate and solid magnesium sulphate heptahydrate maybe obtained in oneor more stages of processes involving the recovery by solution andcooling or refrigeration of sodium nitrate from natural sodiumnitrate-bearings deposits which contain potassium nitrate and magnesiumsulphate associated with the sodium nitrate. The process of the presentinvention permits the separation and separate recovery of sodiumnitrate, potassium nitrate and magnesium sulphate heptahydrate containedin. precipitates obtained by cooling pregnant solutions thus providingfor the recovery of three valuable products from a single product havinglittle value as such. The precipitated products comprise or consistessentially of solid particles or crystals of sodiumnitrate, solidparticles or crystals of potassium nitrate and solid particles orcrystals of magnesium sulphate heptahydrate.

The method or process of the present invention may be employed to eifectseparation of the precipitated sodium nitrate, potassium nitrate andmagnesium heptahydrate and provide concentrate products of relativelypure sodium nitrate, relatively pure potassium nitrate and relativelypure magnesium sulphate heptahydrate. A complete separation operation toincrease the purity of a concentrate with respect to its major componentmay be carried out in a multiple stage operation in which the separatecon-- centrates obtained in any stage may be treated subse quently in.accordance with a process of the invention.

In accordance with a method or process of the inVention, (1) a solidproduct containing potassium nitrate, sodium nitrate and magnesiumsulphate heptahydrate in large proportion or consisting essentially ofpotassium nitrate, sodium nitrate and magnesium sulphateheptahydrate issubjected in the form of an aqueous pulp saturated with respect to thecomponents of the product and containing solid, finely divided particlesof the product in suspension therein to a froth flotation operation inthe presence of an organic cationic flotation reagent which functions asa mineral collecting agent to produce a potassium nitrate concentrate inthe form of a froth and aconcentrate of solid sodium nitrate and solidmagnesium sulphate heptahydrate dispersed in finely divided form in theresidual flotation pulp; (2) the potassium nitrate-bearing frothconcentrate is separated from the residual flotation pulp; (3) thedispersed solid sodium nitrate and solid magnesium sulphate heptahydrateparticles are separated from the liquid phase of the residual pulp, byfiltration or otherwise, to obtain a product comprising a mixture ofsolid particles of sodium nitrate and solid particles of magnesiumsulphate heptahydrate; (4) the resulting mixture of solid particles ofsodium nitrate and magnesium sulphate heptahydrate in the form of a pulpfree of the cationic reagent employed in producing the potassium nitrateconcentrate but saturated with: respect to the componets of the originalproduct comprising potassium nitrate, sodium nitrate and magnesiumsulphate" hept'ahydrate and containing the solid particles of themixture suspended therein is subjected to a froth flotation operation inthe presence of a half ester of a saturated monohydroxy alcohol such,for example, as sodium lauryl sul phate to produce a sodium nitrateconcentrate in the form of a froth and a magnesium sulphate heptahydrateconcentrate in the form of solid particles dispersed inthe residualflotation pulp; (5) the sodium nitrate-beariiligv froth concentrate isseparated from the residual flotation pulp; and (6) the solid magnesiumsulphate heptahydrate particles are separated from the liquid phase ofthe residual flotation pulp to produce a solid magnesium sulphateheptahydrate concentrate.

The liquid phases of the residual flotation pulps may be utilized incarrying out additional froth flotation processes of the invention ofthe types of those of which they are products, or, they may be re-usedin prcoesses of the invention designed to improve the grades orqualities of the various concentrates involving re-treatment of theconcentrates.

An'ysuitable organic cationic reagent may be employed as a mineralcollecting agent in carrying out a method or process of the invention.Salts of alkylamines may be employed advantageously. In employing a.salt of an alkylamine, I prefer to employ a salt in which the alkylradical contains not less than eight and not more than eighteen carbonatoms. Alkylamine acetates may be employed with advantage. I haveemployed octadecylamine acetate with particular advantage.

Any suitable half ester of a saturated monohydroxy alcohol may beemployed as a mineral collecting agent in a process of the invention forproducing the sodium nitrate froth concentrate after separation of thepotassium nitrate froth concentrate and after separation of residualsolids from the liquid phase of the residual pulp and re-pulping of theresidual solids.

For creating or assisting in creating froth at any stage of a process ofthe invention, I may employ any suitable frothing agent, but I prefer toemploy an aliphatic alcohol' having frothing properties. Such alcoholsinclude the isomers of hexyl alcohol containing an isometric methylgroup. Such isomers may be described as methyl amyl alcohols or asmethyl pentanols. The alcohol designated 01 described as3-methyl-1-pentanol or a mixture of methyl amyl alcohols containing asubstantial proportion of that compound may be employed advantageously.

The product to be subjected to the froth flotation treatment may beground to produce solid particles of any suitable sizes. Thus, forexample, satisfactory results may be obtained by grinding to produce afinely. divided product consisting of particles small enough to pass a48-mesh screen. Grinding to produce a; finely divided product consistingessentially of particles small enough to pass a IOO-mesh screen,however, results in economy in reagent costs and in a cleaner separationby froth flotation of the components of the original product.

The froth flotation method of the invention may be carried out with apulp maintained at any suitable temperature. A temperature in the rangeof about 70 F. to 100 F. (or higher or lower if the atmospherictemperature at the point of location of the operation is higher orlower) may be employed advantageously.

' A product of the following composition, typical of precipitatesproduced in sodium nitrate recovery processes, was treated todemonstrate the effectiveness of the process of the invention:

Component: Percent by weight Sodium nitrate 36.0 Potassium nitrate 39.1Magnesium sulphate heptahydrate 23.4 Moisture and impurities 1.5

in carrying out a typical test employing the method of the invention intreating a product of the above-indicated composition, five hundred(500) grams of the solid product were ground in a laboratory pebble millcontaining brine in the form of an aqueous solution saturated withrespect to the components of the product to form a pulp containing aboutsixty percent (60%) by weight of suspended solids consisting essentiallyof particles sufficiently small to pass a lOO-mesh screen. The pulpproduced in the pebble mill was transferred to a laboratory flotationcell and diluted therein with sufficient aqueous solution saturated withrespect to the components of the product undergoing treatment to producea pulp containing about twenty-five percent by weight of suspendedsolids. The diluted pulp was subjected to a froth flotation treatment inthe flotation cell at room temperature in the presence of octadecylamineacetate (CIBHIS'INH2.CH3COOH) in amount equivalent to eight-tenths (0.8)of a pound per ton of suspended solid particles and methyl amyl alcohol(S-methyl-l-pentanol) in amount equivalent to threetenths (0.3) of apound per ton of suspended solid particles. Agitation of the pulp withthe added flotation reagents resulted in the production of a potassiumnitrate froth concentrate substantially immediately. The froth producedwas skimmed from the surface of the pulp in the flotation cell during aperiod of about five minutes. The residual pulp was removed from theflotation cell and filtered to separate the liquid and solid phases. Thefilter cake contained a large proportion of the sodium nitrate andmagnesium sulphate heptahydrate of the original product and constituteda concentrate with respect to the sodium nitrate and magnesium sulphateheptahydrate. The filter cake solids were returned to the flotation celland suspended in an aqueous solution saturated with respect to thecomponents of the original product to form a flotation pulp containingabout twenty percent by weight of suspended solids. The resulting pulpwas subjected to a froth flotation treatment in the flotation cell inthe presence of sodium lauryl sulphate in amount equivalent toeight-tenths (0.8) of a pound per ton of suspended solids and methylamyl alcohol (3-methyl-1- pentanol) in amount equivalent to three-tenths(0.3) of a pound per ton of suspended solids. Agitation of the pulp withthe added flotation reagents resulted in the production of a sodiumnitrate-bearing froth concentrate substantially immediately. The frothproduced was skimmed from the surface of the pulp during a period ofabout five minutes. The residual pulp was removed from the flotationcell and filtered to separate the liquid and solid phases. The filtercake contained a large proportion of the magnesium sulphate heptahydrateof the original product and constituted a concentrate of the magnesiumsulphate heptahydrate with respect to magnesium sulphate heptahydrate(or a tailing product with respect to sodium nitrate and potassiumnitrate).

The following tables show the compositions of the three concentrates andthe distribution of the components of the original product:

TABLE I Magnesium Potassium Sodium Sulphate Percent Nitrate, Nitrate,HeptahybyWelght Percent Percent (irate,

by Weight byWeight Percent by Weight Magnesium Sulphate HeptahydrateConcentrate 23. 4 1. 60 3. 9 94. 2 Potassium Nitrate Concentrate 40. 081. 00 18. 6 0. 7 Sodium Nitrate Concentrate 36. 6 19. 40 77. 4 5. 1

TABLE II Distribution (percent by weight) Magnesium Potassium SodiumSulphate Nitrate Nitrate Heptahydrate Magnesium Sulphate HeptahydrateConcentrate 0. 9 2. 4 94. 2 Potassium Nitrate Concentrate..." 81. 3 20.3 0. 7 Sodium Nitrate Concentrate 17.8 77. 3 5. 1

I claim:

1. The method of separating potassium nitrate, sodium nitrate andmagnesium sulphate heptahydrate contained in a solid product consistingessentially of potassium nitrate, sodium nitrate and magnesium sulphateheptahydrate which comprises subjecting the product in the form of anaqueous pulp saturated with respect to the components of the product andcontaining finely divided particles of the product suspended therein toa froth flotation operation in the presence of a salt of an alkylamineto produce a potassium nitrate concentrate in the form of a froth and aconcentrate of solid sodium nitrate and solid magnesium sulphateheptahydrate dispersed in the flotation pulp, separating the froth fromthe flotation pulp, separating the dispersed solid sodium nitrate andsolid magnesium sulphate heptahydrate from the liquid phase of the pulpto obtain a product comprising a mixture of solid particles of sodiumnitrate and solid particles of magnesium sulphate heptahydrate,subjecting the resulting mixture of solid particles in the form of anaqueous pulp saturated with respect to the components of the originalproduct comprising potassium nitrate, sodium nitrate and magnesiumsulphate heptahydrate and containing the solid particles of the mixturesuspended therein to a froth flotation operation in the presence ofsodium lauryl sulphate to produce a sodium nitrate concentrate in theform of a froth and a magnesium sulphate heptahydrate concentratedispersed in the flotation pulp, and separating the sodium nitrate frothconcentrate from the flotation pulp.

2. The method of separating potassium nitrate, sodium nitrate andmagnesium sulphate heptahydrate contained in a solid product consistingessentially of potassium nitrate, sodium nitrate and magnesium sulphateheptahydrate which comprises subjecting the product in the form of anaqueous pulp saturated with respect to the components of the product andcontaining finely divided particles of the product suspended therein toa froth flotation operation in the presence of a salt of an alkylamineto produce a potassium nitrate concentrate in the form of a froth and aconcentrate of solid sodium nitrate and solid magnesium sulphateheptahydrate dispersed in the flotation pulp, separating the froth fromthe flotation pulp, separating the dispersed solid sodium nitrate andsolid magnesium sulphate heptahydrate from the liquid phase of the pulpto obtain a product comprising a mixture of solid particles of sodiumnitrate and solid particles of magnesium sulphate heptahydrate,subjecting the resulting mixture of solid particles in the form of anaqueous pulp saturated References Cited in the file of this patent withrespect to the components of the original product comprising potassiumnitrate, sodium nitrate and magne- UNITED STATES PATENTS sium sulphateheptahydrate and containing the solid par- 2,120,217 Harris June 7, 1938ticles of the mixture suspended therein to a froth flotation 5 2,297,664Tartaron Sept. 29, 1942 operation in the presence of a half ester of asaturated 2,222,330 Weinig Nov. 19, 1940 monohydroxy alcohol containingnot less than eight and not more than eighteen carbon atoms to produce asodium OTHER REFERENCES nitrate concentrate in the form of a froth and amagnesium sulphate heptahydrate concentrate dispersed in the 10 sflotation pulp, and separating the sodium nitrate froth concentrate fromthe flotation pulp.

3. The method as defined in claim 2 wherein the salt of an alkylamine isan acetate of an alkylamine in which the alkyl radical contains eight toeighteen carbon atoms. 15 4. The method as defined in claim 2 whereinthe salt of an alkylamine is octadecylamine acetate.

Taggart: Handbook of Mineral Dressing, John Wiley & ns, 1945, pp. 12-02;12-14 to 12-18, 12-40 to 12-43; 12-112; 12-116; 12-124, 12-125.

Chemiker Zeitzung, Mar. 1, 1939, No. 17, pp. 148-149, Translation inDivision 55. Soluble Salts, 9 pages.

Russian Patent 47,678, extract translation from Report of the Committeeon Inventions (Vestnik Komitets p0 izolretatel stvu), N0. 7, July 31,1936, in Division 25, 209-166, Soluble Salts, 1 page.

1. THE METHOD OF SEPARATING POTASSIUM NITRATE, SODIUM NITRATE ANDMAGNESIUM SULPHATE HEPTAHYDRATE CONTAINED IN A SOLID PRODUCT CONSISTINGESSENTIALLY OF POTASSIUM NITRATE, SODIUM NITRATE AND MAGNESIUM SULPHATEHEPTAHYDRATE WHICH COMPRISES SUBJECTING THE PRODUCT IN THE FORM OF ANAQUEOUS PULP SATURATED WITH RESPECT TO THE COMPONENTS OF THE PRODUCT ANDCONTAINING FINELY DIVIDED PARTICLES OF THE PRODUCT SUPENDED THEREIN TOFROTH FLOATATION OPERATION IN THE PRESENCE OF A SALT OF AN ALKYLAMINE TOPRODUCE A POTASSIUM NITRATE CONCENTRATE IN THE FORM OF A FROTH AND ACONCENTRATE OF SOLID SODIUM NITRATE AND SOLID MAGNESIUM SULPHATEHEPTAHYDRATE DISPERSED IN THE FLOTATION PULP, SEPARATING THE FROTH FROMTHE FLOTATION PULP, SEPARATING THE DISPERSED SOLID SODIUM NITRATE ANDSOLID MAGNESIUM SULPHATE HEPTAHYDRATE FROM THE LIQUID PHASE OF THE PULPTO OBTAIN A PRODUCT COMPRISING A MIXTURE OF SOLID PARTICLES OF SODIUMNITRATE AND SOLID PARTICLES OF MAGNESIUM SULPHATE HEPTAHYDRATE,SUBJECTING THE RESULTING MIXTURE OF SOLID PARTICLES IN THE FORM OF ANAQUEOUS PULP SATURATED WITH RESPECT TO THE COMPONENTS OF THE ORIGINALPRODUCT COMPRISING POTASSIUM NITRATE, SODIUM NITRATE AND MAGNESIUMSULPHATE HEPTAHYDRATE AND CONTAINING THE SOLID PARTICLES OF THE MIXTURESUSPENDED THEREIN TO A FROTH FLOTATION OPERATION IN THE PRESENCE OFSODIUM LAURYL SULPHATE TO PRODUCE A SODIUM NITRATE CONCENTRATE IN THEFORM OF A FROTH AND A MAGNESIUM SULPHATE HEPTAHYDRATE CONCENTRATEDISPERSED IN THE FLOTATION PULP, AND SEPARATING THE SODIUM NITRATE FROTHCONCENTRATE FROM THE FLOTATION PULP.